1. Field of the Invention
This invention pertains to loading donor or receptor sheets of transfer-imaging material. More particularly, this invention pertains to a method and apparatus for loading a thin flexible film onto an interior surface of an image-processing drum.
2. Description of the Prior Art
In the prior art, it is well known to write onto a film using a laser-imaging system. Such systems include placing a film of material against an inner surface of a generally cylindrical drum. Commonly, such drums have an access opening extending axially along one side of the drum. The axial opening covers about ninety degrees of the cylindrical geometry of the drum such that the drum provides a surface for image exposure over a 270.degree. arc. With such systems, a film would be placed against the internal surface of the drum and held in place by means of a vacuum applied across the drum. To accommodate the vacuum adherence, the drum would be perforated so that a vacuum could be applied to the external surface of the drum with the perforations permitting application of the vacuum to the internal surface of the drum. With the material in place, the film would be scanned with a laser down the center of the drum.
In prior art internal drum laser-imaging systems, films utilized would be relatively thick (for example, about 4 to 6 mils in thickness). A leading edge of the film would be pushed into the drum. The film would assume the internal shape of the drum. After insertion of the film into the drum, the vacuum would be applied to draw the film against the internal surface of the drum.
It is desirable to use thin films with internal drum laser-imaging systems. Thin films present a lower cost of materials for use in the imaging system. Thin films typically are coated polyester material and range in thickness from about 0.25 mils to 2 mils.
The use of thin films within internal drum laser-imaging systems presents serious problems when loading the film. The thin films are extremely flimsy and present a high chance for formation of wrinkles or scratches on the film as it is being placed on the inside surface of the drum. Placement of the film is further complicated due to the need of placing the film against the inner surface of the drum without interfering with laser optics or a scanning-beam transport extending axially within the drum.